In order to provide communication services of high quality in a communication system, a location measurement system for determining a location of a user equipment within a network or locations of entities related to the user equipment more accurately has been required.
Various methods for measuring a location of a user equipment may be roughly divided into two methods. The one is a downlink based location measurement method for measuring the location of the user equipment based on downlink signals transmitted from a base station to the user equipment, and the other one is an uplink based location measurement method for measuring the location of the user equipment based on uplink signals transmitted from the user equipment to the base station. In case of the downlink based location measurement, the user equipment receives downlink signals transmitted from a plurality of cells, and calculates its location by measuring delay time of the downlink signals. On the other hand, in case of the uplink based location measurement, the base station measures the location of the user equipment by measuring delay time of the uplink signals transmitted from the user equipment to the base station and neighboring base station(s). In other words, a geographical location of the user equipment is calculated by basically measuring delay time of signals transmitted from a plurality of cells to the user equipment or delay time of signals transmitted from the user equipment to the plurality of cells. Accordingly, in order to measure the location of the user equipment, a plurality of signals are required. Based on this, various methods for calculating a location of a user equipment are provided. However, it is general that a time difference of arrival (TDOA) scheme or a time of arrival (DOA) scheme is mainly used.
FIG. 1 is a conceptual view illustrating a TDOA scheme for measuring a location of a user equipment.
Referring to FIG. 1, in the TDOA scheme, a base station of a serving cell or anchor cell measures the location of the user equipment by using delay time of signals transmitted from the user equipment to a plurality of cells including the serving cell.
Meanwhile, in order to provide a communication service of high quality, the need of a location measurement scheme for determining a location of a user equipment within a network and/or locations of entities related to the user equipment more exactly has been increased. In this respect, an advanced method for determining a location while minimizing an effect on a structure of an existing radio frame should be provided.